Method and apparatus for continuous ehtylene oxide sterilization

ABSTRACT

A SYSTEM FOR THE CONTINUOUS, IN-LINE STERILIZATION OF   ARTICLES WITH ETHYLENE OXIDE GAS MAINTAINED IN A STERILIZING CHAMBER COMPLETELY CLOSED AND SEALED FROM ATMOSPHERE EXCEPT FOR INLET AND OUTLET TUBES THROUGH WHICH THE ARTICLES ARE CONVEYED. THE TUBES EXTEND ABOVE THE CHAMBER TO PREVENT THE HEAVIER-THAN-AIR GAS FROM ESCAPING.

Sept. 25, 1973 ERNST I 3J$L2Z4 METHOD AND APPARATUS FOR CONTINUOUSETHYLENE OXIDE STERILIZATION Original Filed March 26, 1969 United StatesPatent Int. Cl. A61l13/00 US. C]. 21-58 62 Claims ABSTRACT OF THEDISCLOSURE A system for the continuous, in-line sterilization ofarticles with ethylene oxide gas maintained in a sterilizing chambercompletely closed and sealed from atmosphere except for inlet and outlettubes through which the articles are conveyed. The tubes extend abovethe chamber to prevent the heavier-than-air gas from escapmg.

This is a continuation of application Ser. No. 810,540, filed Mar. 26,1969, now abandoned.

BACKGROUND OF THE INVENTION Field of the inveniton This inventionrelates to a method and apparatus for sterilizing articles with ethyleneoxide gas and more particularly to a continuous sterilizing systemwherein openings are provided in the sterilizing chamber for conveyingarticles into and out of the chamber while at the same time the ethyleneoxide gas is prevented from escaping from the chamber through suchopenings.

Description of the prior art Continuous, gaseous sterilizing apparatuseshave been proposed that provide a sterilizing chamber and conveyingmeans for carrying articles into, through and out of the sterilizingchamber. However, such apparatuses require complex equipment forpreventing the sterilizing gas from escaping from the sterilizingchamber and for preventing air from entering into the chamber.

SUMMARY OF THE PRESENT INVENTION A method and apparatus for thecontinuous sterilization or articles with heavier-than-air ethyleneoxide gas, including a sterilizing chamber, a conveyor for continuouslycarrying articles to be sterilized into, through and out of thesterilizing chamber, and means for preventing escape of the sterilizinggas from the sterilizing chamber. The sterilizing chamber is sealed fromatmosphere except for an inlet tube and an outlet tube, each of which isopen to atmosphere; the tubes extend above the top level of the ethyleneoxide gas in the chamber so as to trap the gas within the sterilizingchamber, wherein the gas is maintained in a substantial quiescentcondition. The conveyor extends into and out of the sterilizing chamberthrough the inlet and outlet tube, respectively. Condensing coils can beprovided in the inlet and outlet tubes to aid in preventing the escapeof ethylene oxide gas from the sterilizing chamber. Control means can beprovided for controlling the concentration and the humidity of thesterilizing gas in the sterilizing chamber. Preliminary to passing intothe sterilizing chamber, the conveyor can extend through an invertedU-shaped tube in which heat and moisture are trapped, forpreconditioning the articles to be sterilized.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be morefully understood 3,761,224 Patented Sept. 25, 1973 DETAILED DESCRIPTIONOF THE PRESENT INVENTION With reference to the drawing, the apparatus ofthe present invention comprises an inverted, U-shaped, preconditioningtube 10, a sterlizing vessel 12 having an inlet tube 14 and an outlettube 16, and a conveyor 18 for carrying the articles to be sterilizedthrough the tube 10, and into, through and out of the sterilizing vessel12.

Referring initially to the sterilizing vessel 12, it is constructed offront and rear walls 20 and 22, respectively, sidewalls 24 and 26, andtop and bottom walls 28 and 30, respectively. The sterilizing vessel 12encloses a sterilizing chamber 32, which chamber is sealed fromatmosphere except for passageways 34 and 36 extending through the inletand outlet tubes 30 and 32 respectively. The passageways 34 and 36 arein fluid communication with the chamber 32, through openings (not shown)in the top wall 28, around which openings the tubes 14 and 16 areconnected.

The inlet tube 14 has an inlet opening 38 and the outlet tube 16 has anoutlet opening 40. The inlet tube 14 is provided with a cold trap or acondenser 42 including cold condensing coils (not shown) adjacent and/orinside of the passageway 34 to help prevent the escape of ethylene oxidegas from the sterilizing chamber 32. A condenser is not absolutelynecessary; a simple cooling coil can be sutficient because the cold highdensity gas tends to run back into the sterilizing vessel 12. Similarly,the outlet tube 16 is provided with a cold trap or a condenser 44including cold condensing coils (not shown) adjacent and/or inside ofthe passageway 36. Condensers and cooling coils are well-known to thoseskilled in the art and any one of a number of different, well-knowncondensers and cooling coils can be used, therefore, the condensers 42and 44 need not be described in detail here.

A controller 46 is connected to the sterilizing vessel 12 through fluidcommunication lines 48 and 50. The controller 46 includes means forsensing and controlling (for example by introducing additionalquantities of ethylene oxide gas) the concentration of the ethyleneoxide sterilizing gas or mixtures of gases, such as the fluorocarbon-12-ETO mixture, within the sterilizing chamber 32, through line 48. Thecontroller 46 also includes means for sensing and controlling thehumidity within the sterilizing chamber 32 through fluid communicationline 50. Control means for sensing and controlling gas and humidityconditions are well-known to those skilled in the art, and such need notbe described in detail herein. A heater means 52 (diagrammaticallyshown) is operatively associated with the sterilizing vessel 12 formaintaining the temperature of the vessel 12 at a predeterminedtemperature or within a predetermined temperature range; the walls ofthe vessel 12 are preferably maintained in the range of 70 to F. Heatingof the vessel 12 can provide increased speed of sterilization and canhelp keep the ethylene oxide gas from condensing out.

The preconditioning tube 10 comprises an inverted U-shaped tube 54having a passageway 56 extending therethrough from a ninlet opening 58at one end thereof to an outlet opening 60 at the other end thereof. Thepreconditioning tube 10 is supported in any suitable manner, such as bysupports 62 and 64, and is preferably positioned with its outlet opening60 aligned with the opening 38 of the inlet tube 14 of the sterilizingvessel 12, but spaced therefrom by an air gap 66; the air gap 66 isdesirable but not necessary. The inverted U-shaped tube 54 is designedso as to trap heat and moisture at its upper portion so as to conditionthe articles to be sterilized, prior to their introduction into thesterilizing chamber 32. A control means 68 is operatively associatedwith the passageway 56 of the tube 54 [for example, by means of a fluidconduit (not shown)] for controlling the temperature and humiditytherein. The heat and moisture control means 68 preferably maintains atemperature within the passageway 56 of between about 130 and 160 F.,and also maintains between about 40% and 70% relative humidity therein.The construction and operation of means for maintaining temperature andhumidity conditions are well-known to those skilled in the art,therefore, a detailed description of control means 68 is not necessary.

The conveyor 18 continuously carries the articles to be sterilize dfroma loading area adjacent the inlet opening 58 of the preconditioning tubeto a discharge area adjacent the outlet opening 40 of the outlet tube 16of the sterilizing vessel 12. The conveyor 18 can be supported withinthe inverted U-shaped tube 54 and within the sterilizing vessel 12 bymeans of brackets 70 or the like. The conveyor 18 is adapted to carryand to continuously move a plurality of baskets 72 adapted to carry thearticles to be sterilized. A control means 74 is provided forcontrolling the speed at which the conveyor 18 moves the baskets 72through the preconditioning tube v10 and the sterilizing vessel 12. Thelength of the preconditioning tube 10 and the length of the conveyor -18in the sterilizing vessel 12 are designed to be sufficient toprecondition and sterilize the articles to be sterilized, by properlyadjusting the speed control means 74. The sterilizing vessel 12 ispreferably a large box-shaped container with a serpentine-shapedconveyor path therein.

Ethylene oxide gas is considerably heavier than air and the apparatus ofthe present invention is designed to take advantage of this fact toentrap the ethylene oxide gas within the sterilizing chamber 32. This isaccomplished by enclosing and sealing the chamber 32 from atmosphereexcept for the inlet and outlet passageways 34 and 36 for the conveyor18, and by positioning at least a portion of the length of thepassageways 34 and 36 above the top level of the gas in the sterilizingchamber 3-2. The sterilizing chamber 32 is preferably completely filledup with sterilizing gas beyond the top wall 28 and up into thepassageways 34 and 36, to levels 76 and 78 therein, respectively. Thecontrol means 46 can include a sensor 80 mounted on each of the tubes 14and 16 (or on just one of the tubes) and having a sensing means (notshown) inside of the passageways 34 and 36, for controlling theintroduction of additional ethylene oxide sterilizing gas into thechamber 32 when the levels 76 and 78 fall below a predeterminedpreferred location. The levels 76 and 78 are air-sterilizing gasinterfaces or boundaries between a layer of sterilizing gas and a layerof air, which layers are stratified as a result of the difference indensity between the two gases. The remainder of the tubes 14 and 16above the interfaces or levels 76 and 78 can take any desired shape, forexample, they can bend back down so that the openings 38 and 40 arepositioned at floor level. The important feature is not where theopenings 38 and 40 are, but that at least a portion of the length ofeach of the passageways 34 and 36 is above the top level of the gas inthe chamber 32, so as to estab lish interfaces 76 and 78 above said toplevel, to trap the sterilizing gas within the chamber 32.

In this manner, a heavier-than-air sterilizing gas can be maintained ina quiescent or substantially quiescent condition and used in acontinuous, in-line, low cost sterilizing process which does not requirecomplex apparatuses and procedures for preventing the escape of thesterilizing gas.

The operation of the present invention is as follows.

The articles to be sterilized are placed in the baskets 72 attached tothe conveyor 18, and carried through the preconditioning tube 10, acrossair gap 66, and into, through and out of the sterilizing chamber 32. Thetime or period of sterilization is controlled by control means 74. Uponleaving the outlet opening 40 of the outlet tube 16, the articles can bemoved to a storage area for any required incubation period.

FIG. 2 shows an embodiment of the present invention in which the tubes14 and 16 are connected to the sidewalls 20 and 22, respectively, of thevessel 12, adjacent the bottom wall 30, whereby the inlet and outletpassageways 34 and 36, respectively, are in fluid communication with thechamber 32 at the bottom of the chamber.

While the present invention has been described with reference to thepreferred embodiment thereof, it is to be understood that the presentinvention is not limited thereto. For example, other heavier-than-airsterilizing gases than ethylene oxide can be used. The preconditioningtube 10 is not an essential part of the present invention; it can beeliminated. Any of a great variety of different types of conveyors canbe used; it is not necessary to use a conveyor of the type shown in thefigure. While in the preferred embodiment the sterilization period iscontrolled by controlling the speed of the conveyor (by means of controlmeans 74), it is also possible to control the sterilization period bycontrolling the length of the conveyor path within the sterilizingchamber 32. In the preferred embodiment of the present invention, thearticles to be sterilized are moved down into the sterilizing chamber 32and up and out of the sterilizing chamber 32 through openings 38 and 40which are positioned higher than or above the top level of thesterilizing gas within the sterilizing chamber. The conveyor 18 can moveintermittently rather than continuously, especially where the vessel 12of the present invention is preferred to be used in a batch typeprocess. It is possible to use other means for introducing and removingthe articles being sterilized than a continuous conveyor. Furthermore,the sterilizing vessel 12 can be provided with a single tube in fluidcommunication with the sterilizing chamber 32, through which tube theconveyor 18 can pass twice, once for carrying incoming articles and oncefor carrying outgoing articles. Also, more than two tubes can beemployed, as for example, when more than one conveyor per sterilizingchamber is used. The tubes 14 and 16 can be connected to the top wall 28as shown or to any of the sidewalls 20-26 or even to the bottom wall 30.

I claim:

1. A sterilizer for sterilizing articles to be sterilized With asterilizing gas comprising:

a sterilizing vessel,

a sterilizing chamber in said vessel and being permanently open toambient,

a quantity of heavier-than-air sterilizing gas in said chamber,

means for maintaining said quantity of heavier-thanair sterilizing gasin said chamber in a quiescent condition, and

means for conveying articles to be sterilized into,

through and out of said sterilizing gas.

2. The apparatus according to claim 1 wherein said conveying meansincludes means for continuously conveying said articles into, through,and out of said chamber.

3. The apparatus according to claim 2 including means for sealing saidchamber from atmosphere except for passageways into said chamber throughwhich said articles are conveyed.

4. The apparatus according to claim 3 including an inlet tube and anoutlet tube each connected to said chamher and having an inlet and anoutlet passageway respectively in fluid communication with said chamber.

5. The apparatus according to claim 4 wherein said inlet and outlettubes are connected to said chamber at the bottom of said chamber forconveying articles to be sterilized into said chamber at the bottom ofsaid chamber and out of said chamber at the bottom of said chamber.

6. The apparatus according to claim 5 including COOIing coils connectedto each of said tubes.

7. The apparatus according to claim 5 wherein each of said tubes andrespective passageways includes a portion thereof positioned above thetop level of said sterilizing chamber.

8. A sterilizer for use with a sterilizing gas comprising:

a sterilizing vessel having a sterilizing chamber adapted to retain aquantity of sterilizing gas,

at least one tube connected to said sterilizing vessel and having apassageway in fluid communication with said sterilizing chamber,

a conveyor, for carrying articles to be sterilized, extending into andout of said sterilizing chamber through said passageway, and

means for controlling the concentration of the sterilizing gas withinsaid sterilizing chamber.

9. The apparatus according to claim 8 wherein said at least one tube isconnected to said vessel at the bottom of said vessel and saidpassageway is in fluid communication with said chamber at the bottom ofsaid chamber.

10. The apparatus according to claim 8 wherein said at least one tubeconsists of two tubes, each of which has a passageway in fluidcommunication with said chamber and wherein said conveyor extends intosaid chamber through one passageway and out of said chamber through theother passageway and including means for completely sealing said chamberfrom atmosphere except for said passageways.

11. A sterilizer for use with a sterilizing gas comprising:

a sterilizing vessel having an enclosed sterilizing chamber adapted toretain a quantity of sterilizing gas;

at least one tube connected to said vessel and having a passageway influid communication with said cham her, said chamber being permanentlyopen to ambient through said passageway, and said passageway having across-sectional area sufiiciently large to allow articles to be conveyedinto and out of said chamber;

means for sealing said chamber from atmosphere except for saidpassageway;

said sterilizing chamber being adapted to retain a quantity ofheavier-than-air sterilizing gas and wherein each of said tubes includesa portion thereof positioned above the top level of said sterilizingchamber such that a length of each of said passageway is also positionedabove said top level; and

means for controlling the concentration of the sterilizing gas withinsaid sterilizing chamber.

12. The apparatus according to claim 11 wherein each of said inlet andoutlet tubes is connected to said chamber at the bottom of said chamber.

13. The apparatus according to claim 11 wherein said at least one tubecomprises an inlet tube and an outlet tube, and including a conveyorpositioned in said inlet and outlet tubes for carrying articles to besterilized into and out of said chamber.

14. The apparatus according to claim 13 wherein said conveyor includesmeans for continuously conveying articles into and out of said chamber.

15. The apparatus according to claim 14 wherein said tubes are connectedto the bottom of said vessel and said passageways are in fluidcommunication with said chamber at the bottom of said chamber.

16. The apparatus according to claim 15 including condensing coilsconnected to said tubes for condensing out any sterilizing gas existingin said passageways above an interface between air and a quantity ofsterilizing gas in said passageways.

17. The apparatus according to claim 16 including means for varying thespeed of said conveyor.

18. The apparatus according to claim 17 including means for heating anysterilizing gas in said sterilizing vessel.

19. The apparatus according to claim 11 including a quantity ofheavier-than-air sterilizing gas filling said chamber up to apredetermined level.

20. The apparatus according to claim 19 wherein said gas is ethyleneoxide.

21. The apparatus according to claim 11 including means for maintainingan interface, between air and said quantity of sterilizing gas, in saidlength of each of said passageways.

22. The apparatus according to claim 21 including condensing coilsconnected to said tubes for condensing out any sterilizing gas existingin said passageways above said interface.

23. The apparatus according to claim 11 including means for varying thespeed of said conveyor.

24. The apparatus according to claim 11 including means for heating saidsterilizing vessel.

25. The apparatus according to claim 11 including an inverted, U-shaped,preconditioning tube positioned adjacent said inlet tube, inspaced-apart relationship thereto, and said conveyor extending throughsaid U-shaped tube and then into said inlet tube.

26. The appartaus according to claim 11 wherein said at least one tubeis connected to said vessel at the bottom of said vessel wherein saidpassageways are in fluid communication with said chamber at the bottomof said chamber.

27. A sterilizer for sterilizing articles to be sterilized with asterilizing gas comprising:

a sterilizing vessel having a sterilizing chamber;

means for maintaining a quantity of a more dense sterilizing gas in saidchamber with a gas-to-gas interface between said sterilizing gas and aless dense first gas located above said sterilizing gas;

means for conveying articles to be sterilized down into said sterilizinggas through said interface, through said sterilizing gas, and up out ofsaid sterilizing gas through said interface; and

means for controlling the concentration of said steri lizing gas withinsaid chamber.

28. A sterilizer for use with a sterilizing gas comprising:

a sterilizing vessel having an enclosed sterilizing chamber adapted toretain a quantity of sterilizing gas;

an inlet and an outlet tube connected to said vessel, and having inletand outlet passageways, respectively in fluid communication with saidchamber;

means for sealing said chamber from atmosphere except for saidpassageways;

a conveyor positioned in said inlet and outlet tubes for carryingarticles to be sterilized into and out of said chamber, respectively;

said sterilizing chamber being adapted to retain a quantity ofheavier-than-air sterilizing gas and wherein each of said tubes includesa portion thereof positioned above the top level of said sterilizingchamber such that a length of each of said passageways is alsopositioned above said top level;

an inverted, U-shaped, preconditioning tube positioned adjacent saidinlet tube, in spaced-apart relationship thereto, and said conveyorextending through said U-shaped tube and then into said inlet tube, and

means for controlling the heat and moisture conditions within saidU-shaped tube.

29. The apparatus according to claim 28 wherein said inlet and outlettubes are connected to the bottom of said vessel such that said inletand outlet passageways are in fluid communication with said chamber atthe bottom of said chamber.

30. The method of sterilizing articles comprising:

conveying articles to be sterilized into and out of an enclosedsterilizing chamber filled with heavier-than-air sterilizing gas throughenclosed inlet and outlet passageways, respectively, extending from aposition above the top level of said chamber down into said chamber, and

maintaining said chamber open to ambient through said passageways duringsaid conveying step and during sterilization of said articles. 31. Themethod according to claim 30 wherein said conveying step comprisesconveying articles into and out of said chamber at the bottom of saidchamber.

32. The method according to claim 30 including maintaining anair-sterilizing gas interface in each of said passageways and above saidtop level.

33. The method according to claim 32 wherein said conveying stepcomprises conveying articles into and out of said chamber at the bottomof said chamber and including sealing said chamber from atmosphereexcept for said passageways.

34. The method according to claim 30 including sealing said chamber fromatmosphere except for said passageways.

35. A method for use in sterilizing articles comprising: maintaining aquantity of a heavier-than-air sterilizing gas in a sterilizing chambersealed from ambient except for the hereinafter recited passageways,

maintaining an inlet and an outlet passageway in fiuid communicationwith said chamber, maintaining at least a portion of said passagewaysabove the top level of said chamber to substantially prevent said gasfrom escaping from said chamber, and

maintaining said chamber permanently open to ambient through saidpassageways.

36. The method according to claim 35 including maintaining said chamberfull of said gas, maintaining an airsterilizing gas interface in saidportion of said passageways, employing for said passageways, passagewaysof suificient cross-sectional area to allow articles to be sterilized tobe conveyed into and out of said chamber through said passageways, andcontrolling the concentration of the sterilizing gas in said chamber.

37. The method according to claim 36 including maintaining said inletand outlet passageways in fluid communication with the bottom of saidchamber.

38. The method of sterilizing articles comprising:

maintaining heavier-than-air sterilizing gas in a quiescent condition ina sterilizing chamber,

continuously conveying articles to be sterilized into said chamber,through said sterilizing gas, and out of said chamber, and preventingsaid sterilizing gas from escaping from said sterilizing chamber.

39. The method of sterilizing articles to be sterilized in a continuousmanner, and with heavier-than-air sterilizing gas, comprising:

conveying said articles through a first enclosed passageway, said firstpassageway extending into a sterilizing chamber from a position abovethe top level of said chamber down into said chamber, said chambercontaining heavier-than-air sterilizing gas,

maintaining said araticles in said chamber and exposed to said gas for apredetermined time period,

conveying said articles up out of said chamber through a second enclosedpassageway extending above said top level,

maintaining said chamber sealed from atmosphere except for saidpassageways, and

maintaining said chamber open to ambient through said passageways duringsaid conveying and maintaining steps.

40. The method according to claim 39 including maintaining said chamberfull of said gas and maintaining an air-sterilizing gas interface ineach of said passageways.

41. The method according to claim 40 wherein said conveying stepscomprise conveying articles into and out of the bottom of said chamberthrough said passageways connecting with the bottom of said chamber.

42. The method according to claim 41 including con- 8 trolling theconcentration of the sterilizing gas in said chamber and controlling thehumidity in said sterilizing chamber.

43. The method accordng to claim 39 including:

controlling the sterilization period by controlling the speed at whichsaid articles are conveyed into and out of said chamber.

44. The method according to claim 39 including:

maintaining said sterilizing chamber at a temperature of between about70 and F.

45. The method according to claim 39 including:

controlling the concentration of the sterilizing gas and the humidity insaid sterilizing chamber.

46. A method for sterilizing articles in a sterilizing gas comprising:

confining a quantity of a sterilizing gas in a chamber open to a firstgas, said sterilizing gas being more dense than said first gas, suchthat a gas-to-gas interface is formed between said sterilizing gas andsaid first gas, and

feeding articles to be sterilized down into said sterilizing gas throughsaid interface, and then up out of said sterilizing gas through saidinterface, to expose said articles to said sterilizing gas. 47. Themethod according to claim 46 wherein said first gas is air and whereinsaid feeding step comprises continuously feeding said articles downinto, through, and up out of said sterilizing gas.

48. The method according to claim 47 including preventing saidsterilizing gas from escaping from said chamber.

49. The method according to claim 47 including maintaining said chamberfull of said sterilizing gas, maintaining said interface in at least onepassageway extending above a top level of said chamber, and maintainingsaid chamber enclosed except for said at least one passageway.

50. The method of sterilizing articles to be sterilized, in a continuousmanner, and with heavier-than-air sterilizing gas, comprising:

conveying said articles through a first enclosed passageway, said firstpassageway extending into a sterilizing chamber from a position abovethe top level of said chamber down into said chamber, said chambercontaining heavier-than-air sterilizing gas, maintaining said articlesin said chamber and exposed to said gas for a predetermined time period,

conveying said articles up out of said chamber through a second enclosedpassageway extending above said top level,

maintaining said chamber sealed from atmosphere except for saidpassageways,

maintaining said chamber full of said gas,

maintaining an air-sterilizing gas interface in each of saidpassageways, and

condensing out sterilizing gas existing in said passageways above saidinterfaces. 51. The method according to claim 50 wherein said conveyingsteps comprise conveying said articles into the bottom of saidsterilizing chamber and conveying articles out of said chamber at thebottom of said chamber.

52. The method of sterilizing articles to be sterilized, in a continuousmanner, and with heavier-than-air sterilizing gas, comprising:

conveying said articles through a first enclosed passageway, said firstpassageway extending into a sterilizing chamber from a position abovethe top level of said chamber down into said chamber, said chambercontaining heavier-than-air sterilizing gas, maintaining said articlesin said chamber and exposed to said gas for a predetermined time period,

conveying said articles up out of said chamber through a second enclosedpassageway extending above said top level,

maintaining said chamber sealed from atmosphere except for saidpassageways, and

preconditioning said articles by conveying said articles through aninverted U-shaped tube prior to conveying them into said chamber, andcontrolling the heat and moisture conditions in said inverted U-shapedtube.

53. The new use of a sterilizer of the continuous type including asterilizing chamber permanently open to atmosphere and a conveyor forcontinuously moving articles to be sterilized into, through and out ofsaid chamber, said new use comprising:

maintaining a quantity of heavier-than-air sterilizing gas in saidchamber in a quiescent condition, and sterlizing articles in saidchamber.

54. The new use of a sterilizer of the continuous type including asterilizing chamber permanently open to atmosphere and a conveyor formoving articles to be sterilized into, through and out of said chamber,said new use comprising:

maintaining a quantity of heavier-than-air sterilizing gas in saidchamber in a quiescent condition, continuously conveying articles to besterilized into,

through and out of said chamber, and

preventing said gas from escaping from said chamber.

55. The new use according to claim 54 wherein said preventing stepcomprises maintaining said chamber sealed from atmosphere except for atleast one passageway and wherein said conveying step comprises conveyingsaid articles through said at least one passageway, and wherein saidpreventing step also comprises maintaining at least a portion of said atleast one passageway above the top level of said sterilizing gas.

56. The new use according to claim 55 including: maintaining anair-sterilizing gas interface in said portion of said passageways.

57. The new use according to claim 54 including maintaining said chambersealed from atmosphere except for an inlet passageway and an outletpassageway, and conveying said articles into and out of said chamberthrough said inlet and outlet passageways, respectively.

58. The new use according to claim 57 wherein said continuouslyconveying step comprises conveying articles into and out of the bottomof said chamber.

59. The new use of a sterilizer of the continuous type including asterilizer chamber and a conveyor for moving articles to be sterilizeddown into, through, and up out of said chamber, said new use comprising:

introducing a quantity of a more dense sterilizing gas into said chambersuch that a gas-to-gas interface is formed between said sterilizer gasand a less dense first gas located above said sterilizing gas, andcontinuously conveying articles to be sterilized down into, through, andup out of said sterilizing gas.

60. The new use according to claim 59 wherein said first gas is air andincluding the step of controlling the concentration of said sterilizinggas in said chamber.

61. The new use of a sterilizer of the continuous type including asterilizing chamber open to atmosphere and a conveyor for movingarticles to be sterilized into, through and out of said chamber, saidnew use comprising:

maintaining a quantity of heavier-than-air sterilizing gas in saidchamber in a quiescent condition, continuously conveying articles to besterilized into,

through and out of said chamber,

preventing said gas from escaping from said chamber,

said preventing step comprising maintaining said chamber sealed fromatmosphere except for at least one passageway,

said conveying step comprising conveying said articles through said atleast one passageway,

said preventing step also comprising maintaining at least a portion ofsaid at least one passageway above the top level of said sterilizinggas,

maintaining an air-sterilizing gas interface in said portion of said atleast one passageway, and

condensing out sterilizing gas present in said at least one passagewayabove said interfaces.

62. The new use according to claim 61 wherein said continuouslyconveying step comprises conveying articles into and out of the bottomof said chamber.

References Cited UNITED STATES PATENTS Re. 20,359 5/1937 Robertson134-11 1,227,101 5/1917 Wehmiller 99214 1,987,414 l/1935 Omsted 993622,273,939 2/1942 Dammers 13411 UX 2,660,512 ll/ 1953 Webster 21-562,704,869 3/1955 Meakin 21-56 X 2,896,640 7/1959 Randall et al 13411 X3,105,335 10/1963 Hickey 21DlG. 4 3,252,405 5/1966 Mencacci 2192 X3,481,691 12/1969 Trainham 21 94 3,501,318 3/1970 Wilson 99--214 X3,088,179 5/1963 Leuthner 21--DIG. 4 3,372,980 3/1968 Satas 21--DIG. 43,547,577 12/1970 Lovercheck 2161 MORRIS O. WOLK, Primary Examiner D. G.MILLMAN, Assistant Examiner US. Cl. X.R. 21-91, DIG. 4

